Synthetic Aperture Radar (SAR) uses well known techniques for increasing azimuthal radar resolution. Azimuthal resolution in radar imaging is ordinarily proportional to the size of the antenna. The physical size required of a conventional radar antenna in order to achieve an azimuthal resolution comparable to the range resolution available from typical radar bandwidths is impractical for use with radar systems carried by aircraft or satellites. SAR uses signal processing technology to replace the function of a large antenna with a small antenna on a moving platform which successively occupies all of the positions which the large antenna would have scanned.
SAR has become important in military and scientific applications. For example, the U.S. Air Force B-1B bomber uses SAR to update its navigation system and to maximize the accuracy of weapons delivery by the aircraft.
The training of SAR operators for such military applications is frequently conducted through the use of simulators. Such simulators require the use of images which accurately represent operational SAR images if the simulations produced thereby are to appear realistic. Under such realistic conditions the operators may gain experience in SAR interpretation as well as learn the functionality of the radar controls and displays. Detailed simulations of flight operations in the contiguous states of the United States provide an ideal application for development of such images which can later be correlated with actual local flight experience.
Presently, it is the practice to use actual SAR images of terrain of interest, obtained by aircraft or satellites, for such operator training. These SAR images, however, are expensive and difficult to obtain. By contrast, aerial or satellite photographs of terrain are comparatively inexpensive and readily available. The United States Geological Survey (USGS), for example, maintains a microfiche index of aerial photographs covering the entire country. The photographs, however, do not provide images that are sufficiently similar to SAR images or that can be conveniently integrated into simulator performance to provide the necessary interoperative realism for flight crew training purposes.
It is desirable therefore to implement a simple, yet inexpensive method for realistically simulating SAR images from such relatively inexpensive and readily available high altitude photographs. The present invention provides such a method.